subcommand restructure and bashstyle refactor. closes #1579

plugins/plugin/subcommands/default

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+plugin_main_cmd() {
+  local desc="shows details about locally installed plugins"
+  local cmd="plugin"
+  plugn version
+  plugn list
+}
+
+plugin_main_cmd "$@"